The present invention concerns the field of decoupling capacitors. Decoupling capacitors on IC packages are often essential to reduce voltage fluctuations, supply charge and maintain integrity of power distribution. Surface Mount Technology (SMT) decoupling capacitors fail to provide decoupling above several hundred megahertz due to their high lead inductance. On-chip capacitors are effective only at gigahertz frequencies due to their low capacitance.
One of the main bottlenecks of transmitting high speed signals through transmission lines is managing the return currents. Wherever there is a return path discontinuity, the noise on the power/ground system gets coupled to the transmission lines. Conversely, any signal current coupling to the power/ground system creates power supply fluctuations. Return path discontinuities could be a major source of noise, such as ground bounce affecting the functionality of the IC, and electromagnetic interference. Discontinuities mainly occur due to signal vias penetrating power/ground planes, transmission lines crossing split power planes, and switching I/O drivers. Decoupling capacitors are essential for power management and handling the return currents to reduce the coupling between the signal transmission and power distribution systems. They are only effective if they are placed close to the return path discontinuity. Therefore, Surface Mount Technology (SMT) decoupling capacitors on a package or board fail to provide decoupling for I/O drivers and receivers above several hundred megahertz due to their high lead inductance. The main focus of this invention is the use of embedded capacitors inside the package to provide I/O decoupling and power supply. The embedded capacitors are formed by using thin dielectrics with high dielectric constant within the layer stack-up of the package.
The bit rates of I/O lines are increasing to provide higher digital bandwidth for processors communicating with, for example, memory chips. As a result of this, decoupling I/O lines is becoming a severe problem.
The present invention provides a solution for charge supply (power delivery) and the decoupling of IC's at the package level. It overcomes the certain inductance problems of the board decoupling methodologies and saves real estate on the chip by reducing the size of the required on-chip capacitance, thereby improving the performance of digital and mixed-signal systems by reducing the power supply noise and providing sufficient current to meet semiconductor switching speed requirements, particularly high current Input/output (I/O) drivers, at a low cost. The present invention has provided capacitors and packages which can provide a low impedance power/ground system close to the I/O drivers up to very high frequencies.